The turbocharger of an internal combustion engine consists of a turbine and a compressor. Hot exhaust gases flow through the turbine to produce work and the work output from the turbine is used as the work input to the compressor. The pressure of ambient air is increased as it flows through the compressor before it enters the engine cylinders. Thus, the purpose of a turbocharger is to increase the pressure of air so that more air gets into the cylinder. Consequently, more fuel can be burned and more power can be produced by the engine. In a turbocharger, exhaust gases enter the turbine at 400°C and 120 kPa at a rate of 0.02 kg/s and leave at 350°C. Air enters the compressor at 50°C and 100 kPa and leaves at 130 kPa at a rate of 0.018 kg/s. The compressor increases the air pressure with a side effect: It also increases the air temperature, which increases the possibility of a gasoline engine to experience an engine knock. To avoid this, an after cooler is placed after the compressor to cool the warm air by cold ambient air before it enters the engine cylinders. It is estimated that the after cooler must decrease the air temperature below 80°C if knock is to be avoided. The cold ambient air enters the after cooler at 30°C and leaves at 40°C. Disregarding any frictional losses in the turbine and the compressor and treating the exhaust gases as air, determine
(a) The temperature of the air at the compressor outlet and
(b) The minimum volume flow rate of ambient air required to avoid knock.

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50°C 100 kPa 350°C Air Turbine Compressor 130 kPa Exhaust gases 30°C Aftercooler Cold air 40 C 400°C 120 kPa